Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$31.80	12.747%	$35.8535	$35.85	$35.85	$35.90
Purchase #2	$112.97	12.497%	$127.0879	$127.09	$127.10	$127.10
Purchase #3	$99.50	13.401%	$112.834	$112.83	$112.85	$112.80
Purchase #4	$36.94	6.369%	$39.2927	$39.29	$39.30	$39.30
Purchase #5	$27.82	8.112%	$30.0768	$30.08	$30.10	$30.10
Purchase #6	$163.91	7.738%	$176.5934	$176.59	$176.60	$176.60
Purchase #7	$40.52	13.206%	$45.8711	$45.87	$45.85	$45.90
7 purchase totals =	$513.46		$567.6094	$567.60	$567.65	$567.70